A review of existing practice |
...an eLib supporting study |
X.500 [X500] is the name given to a series of standards produced by the ISO/ITU-T defining the protocols and information model for a global directory service. X.500 uses a distributed approach based on connected Directory System Agents (DSAs), each of which is a database containing information that is structured according to the X.500 information model. DSAs in the global directory service can exchange data using the Directory System Protocol (DSP). X.500 clients connect to DSAs using the Directory Access Protocol (DAP).
The Lightweight Directory Access Protocol [LDAP], defined by the Internet community (in particular by the IETF ASID working group), was 'designed to provide access to directories supporting the X.500 models, while not incurring the resource requirements of the X.500 Directory Access Protocol (DAP)' [RFC1777]. LDAP is often implemented in 'stand-alone' mode, offering local access to an LDAP-only database without access to the wider X.500 directory.
Both, X.500 and LDAP are primarily used to provide 'white-pages' services - information about people and organisations. However, the X.500 information model also defines object classes representing applications - allowing information to be stored in an X.500 or LDAP database describing network services. Such descriptions were originally designed to describe ISO applications (X.400, FTAM, X.500, etc.) and are not widely used.
The 'applicationEntity' object class definition taken from the 'The COSINE and Internet X.500 Schema' [RFC1274] follows:
applicationEntity OBJECT-CLASS
SUBCLASS OF top
MUST CONTAIN {
commonName,
presentationAddress
}
MAY CONTAIN {
description,
localityName,
organizationName,
organizationalUnitName,
seeAlso,
supportedApplicationContext
}
Andy Powell, UKOLN